...Would-be testers of the tablet-style computer, due to be released Apr. 3, must promise to keep it isolated in a room with blacked-out windows, according to four people familiar with the more than 10-page pact that bars partners from disclosing information about the iPad.

To ensure that it can't be removed, the iPad must also remain tethered to a fixed object, said the people, who asked not to be named because their plans for the iPad have not been made public. Apple won't send out an iPad until potential partners send photographic evidence that they've complied.

Developers want an iPad ahead of the release so they can properly build programs for it. They can run their software on the iPad simulator that Apple makes. But they won't know how the software performs until they're actually using the device.